Field of the Invention
The present invention relates to a piezoelectric material, and in particular, to a lead-free piezoelectric material. The present invention also relates to a piezoelectric element, a multilayered piezoelectric element, a liquid ejection head, a liquid ejection apparatus, an ultrasonic motor, an optical apparatus, a vibration apparatus, a dust removing device, an image pickup device, and an electronic apparatus, all of which use the piezoelectric material.
Description of the Related Art
Typical piezoelectric materials are ABO3 perovskite-type metal oxides such as lead zirconate titanate (hereinafter referred to as “PZT”). However, PZT contains lead in the A-site of the perovskite skeleton. Therefore, the effect of the lead component on the environment has been regarded as a problem. In order to address this problem, piezoelectric materials and piezoelectric elements that include lead-free perovskite-type metal oxides have been proposed.
Examples of the piezoelectric materials that contain a lead-free perovskite-type oxide include barium titanate (BaTiO3) and derivatives thereof. Japanese Patent No. 5217997 discloses a piezoelectric material in which some of the A-sites of barium titanate are substituted with calcium (Ca) and some of the B-sites of barium titanate are substituted with manganese (Mn), iron (Fe), or copper (Cu). The piezoelectric material has an improved temperature-dependent stability of piezoelectric properties at around room temperature and an improved mechanical quality factor, and a piezoelectric element including the piezoelectric material is also disclosed. The improvement in the mechanical quality factor is effective to reduce heat generation during driving of a piezoelectric element and to reduce the power consumption of the piezoelectric element. However, there may be a problem in that the piezoelectric properties of the piezoelectric material disclosed in Japanese Patent No. 5217997 are lower than those of unsubstituted barium titanate (BaTiO3).
As other examples, Japanese Patent Laid-Open No. 2009-215111 and the “Journal of Applied Physics” 2011, Vol. 109, 054110-1 to 054110-6 disclose piezoelectric materials in which piezoelectric properties are improved by substituting some of the A-sites of barium titanate with calcium (Ca) and substituting some of the B-sites thereof with zirconium (Zr). These piezoelectric materials have a low Curie temperature of 80° C. or lower and cause depolarization in a high-temperature environment, for example, in a car in the summer, resulting in a problem of a decrease in piezoelectric properties thereof. In general, piezoelectric properties of a piezoelectric element that has been subjected to a polarization treatment are significantly decreased by depolarization at a temperature 10° C. to 20° C. lower than the Curie temperature. In addition, the piezoelectric material disclosed in Japanese Patent Laid-Open No. 2009-215111 has a small mechanical quality factor.
The present invention provides a lead-free piezoelectric material having a high piezoelectric constant in a wide operating temperature range. The present invention further provides a piezoelectric element, a multilayered piezoelectric element, a liquid ejection head, a liquid ejection apparatus, an ultrasonic motor, an optical apparatus, a vibration apparatus, a dust removing device, an image pickup device, an electronic apparatus, etc., all of which use the piezoelectric material.